I find it very odd. The 2.txt is just the .txt with fewer than 50,000 results. Somehow it seems like Google can read the longer .txt file but not the shorter 2.txt file.
It appears to be a bug in Google Search Console because it randomly happens to many websites. Just to make sure there is nothing else causing problems, do the following:
- Use the Google Search Console Inspector Tool to make sure there is no robots.txt blocking the 2.txt sitemap.
- Make sure the file is UTF-8 encoding.
- Make sure there are only URLs in that file (avoid blank lines, multiple spaces, etc)